Belt for continuously variable transmission and manufacturing method of the same

ABSTRACT

A belt for a continuously variable transmission (CVT) including an endless body and a plurality of V blocks attached to the endless body. The V blocks include a plurality of types of blocks having different thicknesses and are divided into a plurality of V block groups. The V block groups have different ratios of the plurality of types of V blocks, to provide a belt whose noise level is low and dispersed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Apparatuses and methods consistent with the present invention relate toa belt for a continuously variable transmission which is wound across aprimary pulley and a secondary pulley each composed of a pair of sheavesand, more specifically, to a belt for a continuously variabletransmission whose noise is reduced by using V blocks having differentthickness for the large number of V blocks that abut against thepulleys.

2. Description of Related Art

A belt type continuously variable transmission (hereinafter abbreviatedas CVT) is generally used for power transmission systems of cars and thelike. Belts for the CVTs typically include V blocks that arecontinuously attached to an endless body. In terms of the endless body,there is a push-type endless body that uses a ring composed of aplurality of laminated metal plates that transmits power by exerting acompression force on the V blocks, and a pull-type endless body thatuses a chain in which link plates are linked alternately by pins andthat transmits power by a tensile force acting on the chain. Althoughthe present invention has been developed for the push-type endless body,it is also applicable to the pull-type endless body.

Belts for CVTs generate an abutment sound when the V blocks (elements)abut against the pulleys. The sound becomes irritating to human ears ata peak frequency when the thicknesses of the V blocks are the same.

Conventionally, belts have provided a lower noise by dispersing the peakfrequency, described above, by randomly disposing a plurality of typesof blocks having different thicknesses, as disclosed in Japanese PatentPublication No. 1994-21605 and Japanese Patent Laid-Open No.2000-274492, for example. Although the belt in which the blocks, havingdifferent thickness, are attached at random (hereinafter referred to asa randomly mixed belt) can lower the frequency peak by dispersing thenoise, its effect is not enough and a noise is still produced thatirritates human ears.

As shown in FIG. 6, a belt 1 ₁ assembled by 400 blocks (elements) 3having a thickness of only 1.5 mm generates noise having a very narrowpeak on a bite-in order of the blocks to the pulley.

Although a randomly mixed belt 1 ₂, in which the same number (200) ofblocks (elements) having a thickness of 1.4 mm and blocks (elements)having a thickness of 1.5 mm are mixed and arranged at random, can lowerthe frequency peak by white noise centering on an order equivalent to1.45 mm, which is the mean value between 1.4 mm and 1.5 mm as shown inFIG. 7, noise is still generated that is irritating to human ears.

BRIEF SUMMARY OF THE INVENTION

It is an aspect of the invention to provide a belt for a CVT thatdisperses a peak of the frequency and lowers noise by forming aplurality of block groups having different ratios of blocks withdifferent thicknesses.

According to a first exemplary aspect of the invention, there isprovided a belt for continuously variable transmission (CVT) in which anumber of V blocks are attached to an endless body, wherein the V blocksinclude a plurality of types of blocks having different thickness. The Vblocks, which may constitute a large number, comprise a series attachedto the endless body and are divided into a plurality of V block groups,in which combination ratios of the different types of V blocks aredifferent.

That is, multiple V blocks are attached to the endless body and includea plurality of types of V blocks having different thickness. The Vblocks are divided into a plurality of V block groups in which a ratioof different types of V blocks is different. The V blocks attached tothe endless body form a series composed of the plurality of V blockgroups.

The different types of V blocks may be arranged at random in the V blockgroup. The different types of V blocks may also be arranged with aspecified and predetermined order in the V block groups. In addition, anumber of each different type of the V blocks may be almost equal in theseries of the V blocks.

In an exemplary embodiment, the V blocks comprise two types, includingfirst V blocks and second V blocks whose thicknesses are different. Theplurality of V block groups is composed of first and second V blockgroups respectively having a different ratio of the first V blocks tothe second V blocks. The ratios of the first to second V blocks may beinversive in the first and second V block groups. Also, the endless bodymay be a ring in which a plurality of metal sheets is laminated, forexample.

According to a second exemplary aspect of the invention, there isprovided a method for manufacturing a belt for a CVT, comprising forminga plurality of V block groups respectively having a different ratio ofdifferent types of V blocks and forming a series of V blocks byattaching a large number of the V blocks, comprising the plurality of Vblock groups, to an endless belt.

The forming of the V block groups may include dividing the V blocks intothe plurality of V block groups, respectively having a different ratioof different types of V blocks and specifying an arrangement of the Vblocks. The operation of specifying the arrangement may compriseassembling a series of belts, including the V block groups, on acomputer, and simulating a state in which the assembled belts are woundacross pulleys to calculate noise levels of the individual belts, so asto analyze the calculated noise level of each belt to determine anoptimum belt configuration.

According to a further exemplary aspect of the invention, the method formanufacturing the belt for a CVT comprises dividing V blocks into aplurality of V block groups respectively having a different ratio ofdifferent types of V blocks, and specifying a large number ofarrangements of the V blocks in the V block groups to assemble a seriesof belts for simulation on a computer. The belts are simulated in astate in which a large number of the belts are individually wound acrosspulleys to calculate noise levels on the computer, so as to calculatethe noise level of each belt to determine an optimum belt configuration.

Since the belts for a CVT of the present invention are composed of aplurality of V block groups having a different combination ratio of Vblocks, they can disperse noise further when compared to the traditionalrandomly mixed belt and can reduce a rasping noise which is otherwisedisturbing to human ears. The belt may be readily assembled by randomlyarranging the V blocks in the V block groups. The noise may be reducedfurther by arranging the V blocks in the V block groups with apredetermined order that even further reduces the noise level.

The belt may be readily assembled with fewer types of V blocks and itscost lowered by forming the V block groups with two types of V blockshaving different thicknesses and by forming the series of belts usingtwo V block groups.

The number of different types of V blocks used may be equalized, thusimproving efficiency in assembly and yield by equalizing the number of Vblocks in the series or by inverting the ratios of the combinations ofthe V blocks in the two V block groups.

As will be appreciated, the invention may be suitably applied to a beltwhose endless body is a metal ring, such that the V blocks are attachedsuccessively to reduce noise.

Further, the inventive belt manufacturing method enables an optimumarrangement of V blocks, causing less of a noise level, which can beanalyzed through computer simulation, for example.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects of the present invention will be moreapparent by describing certain exemplary embodiments of the presentinvention with reference to the accompanying drawings, in which:

FIG. 1 is a partial perspective view of a CVT belt to which theinvention is applicable.

FIGS. 2A and 2B show a V block, wherein FIG. 2A is a front view and FIG.2B is a side view thereof.

FIG. 3 is a drawing for explaining a randomly mixed belt.

FIG. 4 is a drawing for explaining a combination specified belt.

FIG. 5 is a drawing for explaining a combination and arrangementspecified belt.

FIG. 6 is a drawing for explaining noise levels when the same V blocksare used.

FIG. 7 is a drawing for explaining noise levels of the randomly mixedbelt.

FIG. 8 is a drawing for explaining noise levels of the combinationspecified belt.

FIG. 9 is a chart showing a frequency of appearance during simulation ofthe original belt and the combination specified belt.

FIG. 10 is a flowchart showing a manufacturing method of an exemplaryembodiment of the present invention.

FIG. 11 is a chart showing results obtained by measuring respectivebelts.

FIG. 12 is a table showing an example of a conventional belt.

FIG. 13 is a table showing an example of the combination specified belt.

FIG. 14 is a table showing an example of the combination and arrangementspecified belt.

DETAILED DESCRIPTION OF THE INVENTION

Exemplary modes for carrying out the invention will be explained belowwith reference to the accompanying drawings. FIG. 1 is a perspectiveview showing a part of a CVT belt and FIGS. 2A and 2B show a V block(element). The belt 1 is composed of a ring 2 in which a plurality ofendless metal sheets are laminated and a large number of V blocks(elements) 3 are successively and endlessly attached to the ring 2. Asshown in FIG. 2, in detail, the V block 3 is a plate made of steel, forexample, and has a certain thickness. The V block has a body 5 withV-shaped right and left flanks a that abut against pulleys, and a head 7linked with the body 5 via a pillar 6. A part between the body 5 and thehead 7 on the right and left sides of the pillar 6 is a saddle 9 forreceiving the ring 2. Channels b for flowing lubricant oil are formed onthe right and left flanks a, and the head 7 is provided with a dimple don one face thereof and with a hole e on the other face to maintain theattitude of each block.

In the conventional, randomly mixed belt, a plurality of types of Vblocks 3 having different thickness t are provided. In particular, thereare first V blocks (elements) 3 ₁ whose thickness is 1.4 mm and second Vblocks (elements) 3 ₂ whose thickness is 1.5 mm. The external shape ofthe both blocks 3 ₁ and 3 ₂ is the same. The conventional randomly mixedbelt 12 described above is built by 400 blocks in total wherein 200pieces of a first block 3 ₁ and 200 pieces of a second block 3 ₂ aremixed and arranged at random as shown in FIG. 3.

Contrary to the convention belt, each half of an exemplary embodiment ofa combination specified belt 1 of the present invention is composed of afirst V block group A in which 50 pieces of a first V block 3 ₁ and 150pieces of a second V block 3 ₂ are mixed, and a second V block group Bin which 150 pieces of first V block 3 ₁ and 50 pieces of a second Vblock 3 ₂ are mixed, respectively, as shown in FIG. 4. That is, half ofthe combination specified belt 1 is composed of the first V block groupA in which the first and second V blocks 3 ₁ and 3 ₂ are mixed with aratio of one-to-three and are arranged at random, and the remaining halfis composed of the second V block group B in which the first V blocks 3₁ and the second V blocks 3 ₂ are mixed with a ratio of three-to-one andare arranged at random. It is noted that the ratio of the first andsecond V blocks is not limited to be one-to-three as described above andmay be another ratio such as one-to-two, two-to-three, one-to-fourand-three-to-seven, or the like. Still more, the number of block groupsis not limited to two groups but may be many groups such as three orfour groups, for example. Still more, the number of the blocks havingdifferent thickness is not limited to two but may be more such as threeand four types, for example. It is noted that the number of the first Vblocks is equalized with that of the second V blocks in the whole belt,thus improving efficiency in assembly and yield, by reversing therelationship of the first and second V block groups A and B to set theratio of the first and second blocks as three-to-seven andthree-to-seven, for example.

In an exemplary embodiment of the present invention, as shown in FIG. 5,the combination specified belt can comprise an arrangement specifiedbelt 1 ₁ in which an order (arrangement) of the first blocks 3 ₁ and thesecond blocks 3 ₂ is adequately specified. Each half of the arrangementspecified belt 1 ₁ is formed of a first block group A′ having 60 piecesof a first block 3 ₁ and 140 pieces of a second block 3 ₂, and a secondblock group B′ having 140 pieces of a first block 3 ₁ and 60 pieces of asecond block 3 ₂. The arrangement and order of the first blocks 3 ₁ andthe second blocks 3 ₂ can be specified so as to lower the noise in thefirst and second block groups A′ and B′. Thereby, a dispersion offrequency of appearance of peaks, described later, caused by an order ofthe first and second blocks within each block group may be reduced. Itis noted that although the ratio of the number of the first blocks 3 ₁and the second blocks 3 ₂ has been equalized to be one-to-two(two-to-one) in the first and second block groups A′ and B′ in the belt1 ₁, a different ratio may be used in the both block groups such thatthe ratio is one-to-three in the first block group and is two-to-one inthe second block group, for example.

As described with respect to the conventional technology, a belt 1 ₁composed of only one type of block, e.g., the second blocks 3 ₂ whosethickness is 1.5 mm, generates noise irritating to human ears every timethe blocks bite into the pulleys and has a sharp peak in a very narrowfrequency band, as shown in FIG. 6. The randomly mixed belt 1 ₂ in whichthe same number of first and second blocks 3 ₁ and 3 ₂ are mixed and arearranged at random generates noise whose peak is dispersed and centeredon an order equivalent to the mean value of 1.45 mm and whose width I₁is widened as the peak is lowered, as shown in FIG. 7.

As shown in FIG. 8, the combination specified belt 1 whose half isassembled by the first block group A in which 50 pieces of first block 3₁ and 150 pieces of second block 3 ₂ are mixed and arranged at random(e.g., the ratio of combination is one-to-three) and whose other half isassembled by the second block group B in which 150 pieces of first block3 ₁ and 50 pieces of second block 3 ₂ are mixed and arranged at random(e.g., the ratio of combination is three-to-one) causes random vibrationcentering on the average thickness of 1.475 mm in the first block groupA and causes random vibration centering on the average thickness of1.425 mm in the second block group B. Thereby, as compared to therandomly mixed belt described above, the noise is dispersed further andthe peak is lowered as well. That is, a width I₂ of the peak frequencyis widened more than the width I₁ of the frequency of the randomly mixedbelt, as indicated by a dotted line, and the noise level [dB] is loweredby x [dB] as compared to that of the randomly mixed belt. These featuresrepresent an exemplary effect of the combination specified belt 1.

FIG. 9 is a chart showing simulation results for analyzing simplexvibration which is caused when the combination specified belt bites intothe pulleys, for which a large number of first and second block groups Aand B that are formed on a computer. In FIG. 9, the solid line indicatesresults of the combination specified belt 1 and the broken lineindicates results of the randomly mixed belt 1 ₂, shown in FIG. 7, aftertrying 1,000 different arrangements of V blocks, respectively. In FIG.9, Simplex Vibration [dB] on the axis of abscissas indicates peaks ofsimplex vibration in the simulation of N=K times and Frequency ofAppearance [%] on the axis of ordinates indicates a rate of appearanceof peaks of simplex vibration [dB] in each simulation. It is noted thatthe results of the original belt 1 ₂ simulation represents simplexvibration when the first V blocks whose thickness is 1.4 mm and thesecond V blocks whose thickness is 1.5 mm are combined with a specifiedratio of 50-to-50 and whose arrangement (order) is specified to bedifferent individually. The results of the combination specified belt 1represents simulation of simplex vibration when the first V blocks whosethickness is 1.4 mm and the second V blocks whose thickness is 1.5 mmare used in the same manner. The front half part of the belt is theblock group in which the ratio of a number of the first and second Vblocks is three-to-seven and the rear half part is the block group inwhich the ratio is seven-to-three. Different arrangements may bespecified respectively in each block group.

As shown in FIG. 9, the original belt 1 ₂ has a central value (about30%) where the frequency of appearance is maximized at the simplexvibration b [dB] and the peaks are distributed in a relatively widerange. In contradistinction, the combination specified belt 1 describedabove has a central value (about 57%) where the frequency of appearanceis maximized at the simplex vibration a [dB] and the peaks aredistributed in a relatively narrow range. As compared to the centralvalue b of the original belt described above, the central value a of thecombination specified belt is lower by about 3.2 dB and its height ishigher by about 1.9 times. Still more, its distribution range isnarrower than that of the original belt by about 60%. Accordingly, mostof the combination specified belts 1 cause less noise to be generatedwhen the belts bite into the pulleys, as compared to that of theoriginal (randomly mixed) belt 1 ₂. Statistically, the noise is reducedby about 3.2 dB.

Next, explained is a process in which a combination and arrangementspecified belt having a low simplex vibration is selected among thecombination specified belts.

As shown in FIG. 10, a simulation of a combination and arrangementspecified belt in operations S1 through S5 is carried out. That is,conditions related to the components of the belt, such as the shape ofthe V block, length of the belt and a number of rings, rotationalconditions when the belt is mounted on the CVT and is rotated, such aspulley (sheave) rotational speed and others are set as boundaryconditions for carrying out the simulation in operation S1.

Further, the belt is divided into a plurality of parts and the ratio ofcombination concerning the thicknesses of the V block groups to beattached to the divided parts is set in operation S2. In particular, thebelt is divided into two parts, and the ratio of a number of the first Vblocks (t=1.4 mm) to the second V blocks (t=1.5 mm) is set atthree-to-seven in the first V block group to be attached in the fronthalf part of the belt. The ratio of a number of the first and secondblocks is set at seven-to-three in the second V block group to beattached in the rear half part of the belt.

The arrangement (order) of the first and second V blocks is changed atrandom in the first and second V block groups within the range of theabove rate (ratio) to create a large number of combination andarrangement specified belts on a computer in operation S3. Inparticular, 1,000 arrangement patterns are created. Then, a simulationof the large number of belts, thus created and mounted in a CVT androtated, is carried out to calculate noise levels on the computer inoperation S4.

Then, the noise level calculated per belt described above is analyzed todecide the optimum combination and arrangement specified belt inoperations S5 and S6. For example, the noise level is analyzed by thesound pressure (dB) and a number of belts in that sound level. Thefrequency of appearance [%], as shown in FIG. 9, in operation S5, isdetermined to specify the optimum combination and arrangement specifiedbelt among the analyzed noise levels, i.e., the belt at E in FIG. 9.Thereby, the optimum combination and arrangement specified belt isdecided in the computer simulation with respect to the noise level.

An example of a belt in which the first V blocks and the second V blocksare mixed at random is shown in FIG. 12. An example of the combinationspecified belt composed of the first V block group in which the firstand second V blocks are combined in the ratio of three-to-seven and thesecond V block group in which the first and second V blocks are combinedin the ratio of seven-to-three is shown in FIG. 13. The combination andarrangement specified belt that brought about the best result withrespect to the noise level as the result of computer simulation is shownin FIG. 14.

Next, the results of an actual measurement carried out using theabove-mentioned belts will be explained with reference to FIG. 11. Alarge number of randomly mixed belts 1 ₂, combination specified belts 1and combination and arrangement specified belts 1 ₁ prepared with thecombinations shown in FIGS. 12, 13 and 14 are actually produced. Whileeach belt differs slightly due to allowance, error and others, the beltswere actually wound across the pulleys and operated to measure thegenerated simplex vibration (sound pressure and noise level) [dB]. InFIG. 11, the axis of abscissas represents the actually measured simplexvibration and the axis of ordinates represents frequency of appearance[%] of the belts having the peak value of the simplex vibration of eachbelt. The dotted line indicates the original (randomly mixed) belt 1 ₂,the dotted chain line indicates the combination specified belt 1 and thesolid line indicates the combination and arrangement specified belt 1 ₁.As is apparent from the graph, the maximum value of the frequency ofappearance of the combination specified belt is lower than that of theoriginal belt by 1.5 dB (=d−c) and that of the combination andarrangement specified belt is lower than that by 3.0 dB (=d−e).

Moreover, specifying the arrangement allows the dispersion caused by thearrangement to be reduced. When the dispersion is compared by usingstandard deviation as an index, the deviation σ₁ of the original belt is1.6 dB and that of the combination and arrangement specified belt is 1.1dB. Accordingly, it can be seen that the value of deviation is reducedwhen the arrangement is specified. Still more, in addition to theaverage value being reduced by 3 dB, when values (average value+3σ₁) and(average value+3σ₂) obtained by adding 3σ₁ and 3σ₂ to the average valueof each belt is compared, the combination and arrangement specified beltis lower than the original belt by 4.5 dB. That is, it is shown that thelarge noise level of the original belt may be reduced considerably byspecifying the combination and arrangement of the V blocks.

It is noted that the CVT belt described above used a ring composed oflaminated metal sheets as the endless body however, the invention is notlimited to that and is also applicable, for example, to using a linkchain in which link plates are linked by pins, and the like.

Although illustrative, non-limiting embodiments of the present inventionhave been shown and described, it will be appreciated by those skilledin the art that changes may be made in these embodiments withoutdeparting from the principles and spirit of the invention, the scope ofwhich is defined in the appended claims and their equivalents.

1. A belt for a continuously variable transmission (CVT), said beltcomprising: an endless body; a plurality of V blocks attached to theendless body, wherein, said V blocks include a plurality of types ofblocks having different thicknesses; and said V blocks are divided intoa plurality of V block groups, said V block groups respectively having adifferent ratio of said plurality of types of V blocks.
 2. The belt fora CVT as set forth in claim 1, wherein said different types of V blocksare arranged at random in said V block group.
 3. The belt for a CVT asset forth in claim 1, wherein said different types of V blocks arearranged with a specified and predetermined order in said V blockgroups.
 4. The belt for a CVT as set forth in claim 1, wherein a numberof V blocks of each different type is almost equal in said series of Vblocks.
 5. The belt for a CVT as set forth in claim 1, wherein said Vblocks comprise two types of V blocks including first V blocks andsecond V blocks whose thicknesses are different; and said plurality of Vblock groups is composed of a first V block group and a second V blockgroup respectively having a different ratio of said first V blocks tosaid second V blocks.
 6. The belt for a CVT as set forth in claim 1,wherein the ratio of said first V blocks to said second V blocks isinversive in said first and second V block groups.
 7. The belt for a CVTas set forth in claim 1, wherein said endless body is a ring in which aplurality of metal sheets is laminated.
 8. A belt for a continuouslyvariable transmission (CVT), said belt comprising: an endless body; aplurality of V blocks attached to said endless body, wherein said Vblocks include a plurality of types of V blocks having differentthickness; said V blocks being divided into a plurality of V blockgroups respectively having a different ratio of said different types ofV blocks; and said V block groups are formed from a series of said Vblocks.
 9. A method for manufacturing a belt for a continuously variabletransmission (CVT) in which multiple V blocks of a plurality of typeshaving different thicknesses are attached to an endless body,comprising: forming a plurality of V block groups respectively having adifferent ratio of different types of V blocks; and forming a series ofV blocks by attaching a plurality of V blocks to the endless belt toprovide said plurality of V block groups.
 10. The method formanufacturing the belt for a CVT as set forth in claim 9, whereinforming said V block groups comprises: dividing said V blocks into aplurality of the V block groups, the V block groups respectively havinga different ratio of different types of the V blocks; and specifying anarrangement of said V blocks in said V block groups; and said specifyingan arrangement comprises, assembling a series of belts using said Vblock groups on a computer; simulating a state in which said assembledbelts are respectively wound across pulleys to calculate a noise level;and analyzing the calculated noise level of each belt to determine anoptimum belt.
 11. A method for manufacturing a belt for a continuouslyvariable transmission (CVT), comprising: dividing V blocks into aplurality of V block groups which respectively have a different ratio ofdifferent types of V blocks; specifying a plurality of arrangements ofsaid V blocks for said V block groups so as to assemble a series ofindividual belts on a computer; simulating a state in which saidplurality of assembled belts is wound across pulleys to calculate anoise level of the individual belts on the computer; and analyzing thecalculated noise level of each belt to determine an optimum belt.